The conventional operating method for determining the boold pressure, called the RIVA-ROCCI method, consists in blocking part of the circulatory system of the sick person by exerting on his arm a pressure greater than the systolic pressure so as to prevent the blood from flowing towards the fore-arm, then in very slowly releasing this pressure while reading from a pressure gauge the two values at which the KOROTKOV noises appear, grow fainter then disappear.
When the noises appear, the peak pressure or systolic pressure is noted; when the noises disappear, the minimum preassure or diastolic pressure is noted.
A first disadvantage of this method is that it requires, in addition to a stethoscope, an inflatable space-consuming arm band whose dimensions must be adapted to the size of the arm.
A second drawback of this method is that the relation bewteen the diastolic pressure, which is however the most representative of the circulatory condition of the sick person, and the dying away or total disappearance of the KOROTKOV noises is very widely debated in the medical sphere.
A third drawback of this method is that the parasite noises emitted in the room or caused by a movement of the patient makes listening to the KOROTKOV noises a delicate operation and require an experienced operator.
Numerous improvements have been proposed, consisting essentially in making the inflation of the arm band, the measurement of the pressure or the analysis of the noises automatic, such for example as in patent FR 75 05046 (published under the number 2.260.975), but they generally lead to a heavy, space-consuming and uncertain aparatus.